The key objective of this proposal is to provide protected time for the applicant to serve as a mentor for students, trainees, and junior faculty. The mentoring vehicle will consist of two research projects focusing on the effects of male sex hormones on breathing during sleep and the determinants of long term-facilitation during sleep. The research plan is focused on the effects of male sex hormones on breathing during sleep. The specific aims are: 1. To investigate the occurrence and determinants of LTF in sleeping humans. We hypothesize that LTF can be activated by repetitive hypoxia in sleeping humans especially subjects with snoring and inspiratory flow limitation. 2. To determine whether LTF results in increased pharyngeal caliber and amelioration of inspiratory flow limitation. We hypothesize that LTF has a preferential effect on upper airway dilating muscle activity relative to thoracic pump muscles and hence it "unloads" the upper airway by reducing upper airway resistance. 3. To investigate the effect of REM sleep on upper airway patency. We hypothesize that pharyngeal patency is preserved during REM sleep both at the retropalatal and retroglossal levels. The mentoring plan will be individualized based on the career stage and objectives. Students will receive a focused curriculum with specific assignments to enhance research interest and nurture critical thinking ability. The mentoring process for pre-doctoral fellows will emphasize specific research skills including public presentation, scientific write up, and scientific debate including understanding the limitations of methodology and extrapolation. The focus in post-doctoral fellows and junior faculty will be to nurture independent research leading to an independent (more aptly called, "interdependent") research program. The work environment is outstanding and the institutional commitment is superb.